Molded foam

ABSTRACT

A molded foam that can be easily taken out of split mold blocks is provided. According to an aspect of the present disclosure, a molded foam is obtained by clamping, with split mold blocks, foamed resin obtained by melting and kneading a polyethylene-based resin, wherein the molded foam has a MFR (190° C., g/10 min) of less than 0.8, or the polyethylene-based resin has a MFR (190° C., g/10 min) of not more than 1.0.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a U.S. national phase application under 35 U.S.C. § 371 ofInternational Patent Application No. PCT/JP2014/082394, filed on Dec. 8,2014, and claims benefit of priority to Japanese Patent Application No.2013-272421, filed Dec. 27, 2013. The entire contents of theseapplications are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a molded foam molded from foamed resinin molten state.

BACKGROUND ART

In air conditioning devices for automobiles, for example, tubularair-conditioning ducts are used for ventilating air.

An air-conditioning duct using a molded foam is known. The molded foamincludes foamed resin obtained by foaming thermoplastic resin using afoaming agent. The molded foam makes it possible to achieve both highthermal insulating property and light weight. Accordingly, there is agrowing demand for molded foams.

As a method for manufacturing a molded foam, blow molding method iswidely known which includes blowing air into molten foamed resin beingclamped by split mold blocks, and expanding the resin.

In an example of technical literature of an application filed prior tothe present invention, Japanese Unexamined Patent ApplicationPublication No. 2005-241157A discloses a foamed duct molded by foamedblow molding which includes adding supercritical fluid as a foamingagent, wherein the foamed duct has an outer surface roughness andexpansion ratio within predetermined ranges.

Japanese Patent No. 4084209B2 discloses a technology for forming afoamed layer by foaming a foamed layer base material resin using aphysical foaming agent. As the foamed layer base material resin, a resinobtained by compounding a specific high-density polyethylene and aspecific low-density polyethylene at a specific ratio is used.

SUMMARY OF THE INVENTION

In Japanese Unexamined Patent Application Publication No. 2005-241157A,an example is disclosed in which polypropylene-based resin is used asraw material resin for the foamed duct. As the raw material resin for amolded foam, polypropylene-based resin is commonly used, as described inJapanese Unexamined Patent Application Publication No. 2005-241157A. Thepolypropylene-based resin, however, has high raw material cost.Accordingly, in recent years, polyethylene-based resin has been used insome cases as the raw material resin for molded foam, as described inJapanese Patent No. 4084209B2. The polyethylene-based resin raw materialis typically less expensive than the polypropylene-based resin rawmaterial. Thus, the polyethylene-based resin raw material enablesmanufacture of a molded foam at reduced cost.

The present inventors have attempted to obtain a desired molded foam byusing polyethylene-based resin as molded foam raw material resin.

It turned out, however, that, depending on the polyethylene-based resinused as the molded foam raw material resin, the resin constituting themolded foam sometimes becomes attached to split mold blocks when themolded foam that has been molded while being clamped by the split moldblocks is taken out of the split mold blocks. As a result, the moldedfoam cannot be easily removed from the split mold blocks. Accordingly,there is a need for taking out the molded foam from the split moldblocks easily.

An object of the present disclosure is to provide a molded foam that canbe easily taken out of split mold blocks.

According to an aspect of the present disclosure, there is provided amolded foam molded by clamping, by split mold blocks, a foamed resinobtained by melting and kneading a polyethylene-based resin. The moldedfoam has a MFR (190° C., g/10 min) of less than 0.8, or thepolyethylene-based resin has a MFR (190° C., g/10 min) of not more than1.0.

According to the present invention, a molded foam that can be easilytaken out of the split mold blocks can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an instrument panel duct 1 according to anexample.

FIG. 2 depicts a part of the instrument panel duct 1 around a fittingportion 102 d thereof.

FIG. 3 is a cross sectional view taken along D-D′ of FIG. 2.

FIG. 4 is a first diagram illustrating an exemplary molding method forthe instrument panel duct 1 according to the present example.

FIG. 5 is a second diagram illustrating the exemplary molding method forthe instrument panel duct 1 according to the present example.

FIG. 6 is a third diagram illustrating the exemplary molding method forthe instrument panel duct 1 according to the present example.

FIG. 7 depicts parts around the fitting portion 102 d being clamped bysplit mold blocks.

FIG. 8 is a diagram illustrating another exemplary molding method.

FIG. 9 is a chart of examples and comparative examples.

DETAILED DESCRIPTION OF THE INVENTION Outline of Molded Foam 1 Accordingto an Aspect of the Present Disclosure

With reference to FIG. 1 and FIG. 9, the outline of an example of amolded foam 1 according to an aspect of the present disclosure will bedescribed. FIG. 1 depicts a configuration example of the molded foam 1according to an aspect of the present disclosure. FIG. 9 is a chart fordescribing the molded foam 1 according to an aspect of the presentdisclosure.

The molded foam 1 according to an aspect of the present disclosure ismolded by clamping foamed resin with split mold blocks. The foamed resinis obtained by melting and kneading polyethylene-based resin. The moldedfoam 1 according to an aspect of the present disclosure is characterizedin that, as indicated in FIG. 9, the molded foam 1 obtained by moldinghas a melt flow rate (MFR; 190° C., g/10 min) of less than 0.8, or thepolyethylene-based resin has a MFR (190° C., g/10 min) of not more than1.0.

When the MFR of the molded foam 1 obtained by molding is set to be lessthan 0.8, or when the MFR of the polyethylene-based resin is set to benot more than 1.0, the foamed resin constituting the molded foam 1 canbe prevented from becoming attached to the split mold blocks when themolded foam 1 is removed from between the split mold blocks.Accordingly, the molded foam 1 can be easily taken out of the split moldblocks. In the following, an example of the molded foam 1 according toan aspect of the present disclosure will be described in detail withreference to the attached drawings. In the following description of theexample, an instrument panel duct 1 will be described as an example ofthe molded foam 1.

<Configuration Example of Instrument Panel Duct 1>

With reference to FIG. 1 to FIG. 3, a configuration example of theinstrument panel duct 1 according to the present example will bedescribed. FIG. 1 is a schematic plan view of the instrument panel duct1. In FIG. 1, there is illustrated the side of the instrument panel duct1 on which a supply portion 105 for connecting an air conditioner unit(not illustrated) is provided. FIG. 2 is a schematic plan view of a partaround a fitting portion 102 d illustrated in FIG. 1. FIG. 3 is a crosssectional view taken along D-D′ of FIG. 2.

The instrument panel duct 1 according to the present example is alightweight instrument panel duct for allowing cool or warm air suppliedfrom the air conditioner unit to be circulated to desired locations.

The instrument panel duct 1 according to the present example is moldedby blow-molding foamed resin clamped by split mold blocks. The foamedresin is obtained by melting and kneading predeterminedpolyethylene-based resin.

The instrument panel duct 1 according to the present example has anexpansion ratio of 1.3 or more. The instrument panel duct 1 has a closedcell structure with a plurality of cells (having a closed cell contentof 70% or more). The instrument panel duct 1 has an average thickness of0.5 mm or more. The instrument panel duct 1 has a duct inner surfacewith a surface roughness Rmax of 200 μm or less. When the surfaceroughness Rmax is 200 μm or less, an increase in ventilation efficiencycan be achieved. Preferably, the instrument panel duct 1 according tothe present example has a tensile fracture elongation at −10° C. of 40%or more, and a tensile elastic modulus at normal temperature of 1000kg/cm² or more. Preferably, the tensile fracture elongation at −10° C.may be 100% or more. The terms used in the present example are definedin the following.

Expansion ratio: The expansion ratio is defined as a value obtained bydividing the density of foamed resin used for a molding method of thepresent example that will be described later, by the apparent density ofa tube body X1 (see FIG. 3) of the instrument panel duct 1 obtained bythe molding method of the present example.

Tensile fracture elongation: A part of the tube body X1 of theinstrument panel duct 1 obtained by the molding method of the presentexample as will be described below is cut out. The cut-out part isstored at −10° C., and, using the part as a No. 2 test specimen inaccordance with JIS K-7113, the tension speed is measured at 50 mm/min.The resultant value is defined as the tensile fracture elongation.

Tensile elastic modulus: A part of the tube body X1 of the instrumentpanel duct 1 obtained by the molding method of the present example aswill be described below is cut out. Using the part as a No. 2 testspecimen at normal temperature (for example, 23° C.) in accordance withJIS K-7113, the tension speed is measured at 50 mm/min. The resultantvalue is defined as the tensile elastic modulus.

As illustrated in FIG. 1, one end of tube portions 101 (101 a to 101 d)of the instrument panel duct 1 according to the present example isprovided with a supply portion 105 to be connected to an air conditionerunit (not illustrated). The other end of the tube portions 101 (101 a to101 d) is provided with a fitting portions 102 (102 a to 102 d). Thetube portions 101 (101 a to 101 d), the supply portion 105, and thefitting portions 102 (102 a to 102 d) constitute a tube body X1 (seeFIG. 3) to which flange portions 103 (103 a to 103 g) are connected.

In the present example, an “average thickness” refers to the average ofthickness values of the molded article measured at equal intervals ofapproximately 100 mm along a hollow extension direction of the moldedarticle. For example, the thickness is measured of two wall portions ofa hollow molded article that are welded via a parting line, each at aposition along a direction perpendicular to the parting line, and anaverage value of the measured thicknesses provides the averagethickness. The measurement positions are selected so as not to includethe flange portions 103 and the like.

The inside of the tube body X1 is configured with a flow passageway forcirculating fluid so as to allow cool or warm air from the airconditioner unit to be circulated therethrough.

The flow passageway for the fluid supplied from an opening portion 111of the supply portion 105 into the tube body X1 is divided into fourflow passageways A, B-1, B-2, and C, as illustrated in FIG. 1. The fluidsupplied via the opening portion 111 of the supply portion 105 into thetube body X1 flows out of the opening portion of the fitting portion 102a via the flow passageway A. The fluid also flows out of the openingportion of the fitting portion 102 b via the flow passageway B-1. Thefluid also flows out of the opening portion of the fitting portion 102 cvia the flow passageway B-2. In addition, the fluid flows out of theopening portion of the fitting portion 102 d via the flow passageway C.

The configuration of the instrument panel duct 1 around the flowpassageway A includes the supply portion 105 provided at one end of thetube portion 101 a, with the fitting portion 102 a provided at the otherend thereof. To the tube body X1 configured with the tube portion 101 a,the supply portion 105, and the fitting portion 102 a, the flangeportions 103 a and 103 e are connected. The flange portion 103 a isprovided with an affixing hole 107 a for affixing the instrument panelduct 1 to another tubular member connected by the fitting portion 102 a.By inserting a bolt, which is not illustrated, through the affixing hole107 a and fastening the bolt with a nut, the instrument panel duct 1 canbe affixed with respect to the other tubular member. The flange portion103 e is also provided with an affixing hole 107 e.

The configuration of the instrument panel duct 1 around the flowpassageway B-1 includes the supply portion 105 provided at one end ofthe tube portion 101 b, with the fitting portion 102 b provided at theother end thereof. To the tube body X1 configured with the tube portion101 b, the supply portion 105, and the fitting portion 102 b, the flangeportion 103 b is connected. The flange portion 103 b is provided with anaffixing hole 107 b for affixing the instrument panel duct 1 to anothertubular member connected by the fitting portion 102 b.

At a narrow interval portion between the tube portions 101 a and 101 b,a bridge portion 104 e for maintaining strength is provided andconnected with the tube portions 101 a and 101 b.

The configuration of the instrument panel duct 1 around the flowpassageway B-2 is similar to the configuration around the flowpassageway B-1 described above.

The configuration of the instrument panel duct 1 around the flowpassageway C is similar to the configuration around the flow passagewayA described above.

Between the tube portions 101 b and 101 c, the flange portion 103 g isprovided and connected with the tube portions 101 b and 101 c. Theflange portion 103 g is also provided with an affixing hole 107 g.

As illustrated in FIG. 1, the instrument panel duct 1 according to thepresent example has the tube body X1 (see FIG. 3) with the flangeportions 103 (103 a to 103 g) connected to the outside thereof. The tubebody X1 refers to the portion including the tube portions 101 (101 a to101 d), the supply portion 105, and the fitting portions 102 (102 a to102 d).

In the instrument panel duct 1 according to the present example, theopening portions 100 of the fitting portions 102 have an opening areagreater than the opening area of the tube portions 101. The opening areaof the tube portions 101 refers to the area of an opening portion of thetube portions 101 in a section taken along a direction perpendicular tothe direction in which the flow passageway of the instrument panel duct1 extends. The opening area of the opening portions 100 of the fittingportions 102 can be made greater than the opening area of the tubeportions 101 by, for example, configuring the fitting portions 102 inbell shape. The bell shape refers to a shape with increasingly greateropening area toward the opening end.

<Exemplary Molding Method for Instrument Panel Duct 1>

With reference to FIG. 4 to FIG. 6, an exemplary molding method for theinstrument panel duct 1 according to the present example will bedescribed. FIG. 4 is a side view of split mold blocks in open state.FIG. 5 is a side view of the split mold blocks in closed state. FIG. 6is a cross sectional view of the two split mold blocks in closed statetaken along a contact surface thereof as viewed from a split mold block12 a side.

As illustrated in FIG. 4, a cylindrical foamed parison 13 obtained byinjecting foamed parison from an annular die 11 is extruded between thesplit mold blocks 12 a and 12 b.

The split mold blocks 12 a and 12 b are then clamped, whereby, asillustrated in FIG. 5, the foamed parison 13 is sandwiched between thesplit mold blocks 12 a and 12 b. In this way, the foamed parison 13 isstored in cavities 10 a and 10 b of the split mold blocks 12 a and 12 b.

Then, as illustrated in FIG. 5 and FIG. 6, with the split mold blocks 12a and 12 b clamped, a blow-in needle 14 and blow-out needles 15 aresimultaneously pierced into the foamed parison 13, thereby piercingpredetermined holes provided in the split mold blocks 12 a and 12 b. Asthe tips of the blow-in needle 14 and blow-out needles 15 enter thefoamed parison 13, compressed gas, such as compressed air, isimmediately blown into the foamed parison 13 via the blow-in needle 14.The compressed gas passes through the foamed parison 13 and is blown outvia the blow-out needles 15. In this way, blow molding is performed atpredetermined blow pressure.

The blow-in needle 14 pierces the position corresponding to the openingportion 111 of the supply portion 105 of the instrument panel duct 1illustrated in FIG. 1. Thus, a blow-in opening for blowing thecompressed gas into the foamed parison 13 is formed. The blow-outneedles 15 pierce the positions corresponding to the opening portions100 (100 a to 100 d) of the fitting portions 102 (102 a to 102 d) of theinstrument panel duct 1 illustrated in FIG. 1. Thus, blow-out openingsfor blowing out the compressed gas from inside the foamed parison 13 tothe outside are formed.

Accordingly, the compressed gas can be blown into the foamed parison 13via the blow-in needle 14. The compressed gas passes through the foamedparison 13 and is blown out of the blow-out needles 15. In this way,blow molding can be performed at predetermined blow pressure.

According to the present example, the compressed gas is blown into thefoamed parison 13 from the blow-in needle 14, and discharged out of thecavities 10 a and 10 b of the split mold blocks 12 a and 12 b. Thisproduces a negative pressure state in the gap between the foamed parison13 and the cavities 10 a and 10 b. As a result, a pressure difference isset (i.e., the pressure inside the foamed parison 13 becomes higher thanthe external pressure) between the inside and outside of the foamedparison 13 stored in the cavities 10 a and 10 b in the split mold blocks12 a and 12 b. Accordingly, the foamed parison 13 is pressed onto wallsurfaces of the cavities 10 a and 10 b.

In the above-described molding step, the step of blowing the compressedgas into the foamed parison 13 and the step of producing a negativepressure outside the foamed parison 13 may not be performedsimultaneously, and may be performed at different times.

According to the present example, as illustrated in FIG. 7, the foamedparison 13 is clamped by the split mold blocks 12 a and 12 b withpressing force Z. Accordingly, as described above, the portion of thefoamed parison 13 corresponding to the tube body X1 is pressed onto thecavities 10 a and 10 b at predetermined blow pressure. At the same time,the portions corresponding to the board-like portion Y1 of the flangeportions 103 (103 a to 103 g) and the bridge portions 104 (104 e and 104f) are pressed in the thickness direction and compressed to thethickness between the cavities 10 a and 10 b of the split mold blocks 12a and 12 b.

For the portion of the foamed parison 13 corresponding to the tube bodyX1, compressed gas, such as compressed air, is blown from the blow-inneedle 14 into the foamed parison 13 as described above. The compressedgas passes through the foamed parison 13 and is blown out of theblow-out needles 15. Then, the foamed parison 13 is pressed onto thecavities 10 a and 10 b by predetermined blow pressure for apredetermined time, and 50% to 80% of the foamed parison 13 from theside of the cavities 10 a and 10 b in the thickness direction of thetube body X1 is cooled and solidified. Thereafter, the remaining foamedparison 13 in molten state is allowed to naturally solidify while beingclamped by the split mold blocks 12 a and 12 b without performingcooling with compressed gas.

The temperature of the compressed gas supplied from the blow-in needle14 into the foamed parison 13 for cooling is set to 10° C. to 30° C. andpreferably room temperature (for example, 23° C.). By setting thecompressed gas temperature to room temperature, the need for providing atemperature adjustment facility for adjusting the compressed gastemperature can be eliminated. Consequently, the instrument panel duct 1can be molded at lower cost. On the other hand, a temperature adjustmentfacility may be provided to lower the temperature of the compressed gassupplied from the blow-in needle 14 into the foamed parison 13 belowroom temperature, whereby the time for cooling the instrument panel duct1 can be reduced. The time (i.e., duration of application) for coolingby compressed gas may preferably be not more than 35 seconds, dependingon the compressed gas temperature. In this way, approximately 50% to 80%of the foamed parison 13 from the side of the cavities 10 a and 10 b inthe thickness direction of the tube body X1 can be cooled and solidifiedwhile the foamed parison 13 is maintained in molten state on the innersurface side of the tube body X1. Thereafter, the remaining foamedparison 13 in molten state can be allowed to naturally solidify whilebeing clamped by the split mold blocks 12 a and 12 b without performingcooling by compressed gas.

The resin that may be used for molding the instrument panel duct 1according to the present example is preferably foamed resin obtained bymelting and kneading predetermined polyethylene-based resin so that theMFR of the instrument panel duct 1 as a molded article becomes less than0.8. When the MFR of the instrument panel duct 1 as a molded article is0.8 or more, it may become impossible to obtain the instrument panelduct 1 having high surface roughness, ease of removal, and ease ofdeburring. In order to measure the MFR value, resin is obtained byheating and melting and thereby defoaming a sample piece cut out of themolded article, and the resin is measured at a test temperature of 190°C. and with test load of 2.16 kg according to JIS K-7210. The surfaceroughness, ease of removal, and ease of deburring will be described withreference to examples that will be described below.

The polyethylene-based resin forming the foamed resin is formed bymelting and kneading a polyethylene-based elemental resin, ahigh-density polyethylene-based elemental resin, a blend resin obtainedby mixing a plurality of low-density polyethylene-based resins, a blendresin obtained by mixing a plurality of high-density polyethylene-basedresins, and a blend resin obtained by mixing a low-densitypolyethylene-based resin and a high-density polyethylene-based resin. Inthis case, the MFR (190° C., g/10 min) of the polyethylene-based resinfor forming the foamed resin is not more than 1.0.

For example, when the foamed resin is formed using twopolyethylene-based resins, the MFRs of the two polyethylene-based resinsare set such that the MFR obtained by a calculation process performed onthe mixture ratios of the two polyethylene-based resins satisfies thefollowing Expression 1:A×X/100+B×Y/100≤1.0  Expression 1where

A is the MFR of the first polyethylene-based resin;

B is the MFR of the second polyethylene-based resin;

X is the mixture ratio of the first polyethylene-based resin forming thefoamed resin;

Y is the mixture ratio of the second polyethylene-based resin formingthe foamed resin; and

X+Y=100.

It may be more preferable to form the foamed resin usingpolyethylene-based resin manufactured by autoclave process than usingpolyethylene-based resin manufactured by tubular process. This isbecause the expansion ratio of the instrument panel duct 1 as a moldedarticle can be made higher by using the polyethylene-based resinmanufactured by autoclave process than by using the polyethylene-basedresin manufactured by tubular process. The MFR of the low-densitypolyethylene-based resin is preferably 1.0 to 3.0.

The foamed resin used for molding the instrument panel duct 1 may alsobe formed using pulverized material obtained by pulverizing the burrproduced during the molding of the instrument panel duct 1. In thiscase, rather than forming the foamed resin solely with 100% pulverizedmaterial, it may be more preferable to form the foamed resin by meltingand kneading the pulverized material and virgin material. The virginmaterial refers to unused resin. As such resin, according to the presentexample, the above-described polyethylene-based resin is used. By usingvirgin material, degradation of the resin constituting the instrumentpanel duct 1 can be avoided. When pulverized material and virginmaterial are melted and kneaded to form foamed resin, the ratio of thepulverized material to virgin material that are melted and kneaded maybe 90% to 10%.

Examples of the foaming agent that may be applied when molding theinstrument panel duct 1 according to the present example includephysical foaming agents, chemical foaming agents, and mixtures thereof.Examples of the physical foaming agents include inorganic physicalfoaming agents such as air, carbonic acid gas, nitrogen gas, and water;organic physical foaming agents such as butane, pentane, hexane,dichloromethane, and dichloroethane; and supercritical fluids thereof.Preferably, the instrument panel duct may be fabricated using carbondioxide, nitrogen, or the like as supercritical fluid. When nitrogen isused, the instrument panel duct may be fabricated by setting thecritical temperature at −149.1° C. or above, and the critical pressureat 3.4 MPa or above. When carbon dioxide is used, the instrument panelduct may be fabricated by setting the critical temperature at 31° C. orabove and the critical pressure at 7.4 MPa or above.

After the molding, the instrument panel duct 1 is taken out of the splitmold blocks 12 a and 12 b. Specifically, the split mold blocks 12 a and12 b are opened with the burrs formed on top of the instrument panelduct 1 being gripped by a predetermined machine (such as clips). Theinstrument panel duct 1 is then removed from between the split moldblocks 12 a and 12 b.

Then, unwanted portions, such as burrs, formed around the instrumentpanel duct 1 taken out of the split mold blocks 12 a and 12 b areremoved. In this way, the instrument panel duct 1 having a complex shapeas illustrated in FIG. 1 can be obtained.

As illustrated in FIG. 1, in the vicinity of all of the opening portions100 (100 a to 100 d) and 111 formed on the fitting portions 102 (102 ato 102 d) and the supply portion 105 constituting the tube body X1 ofthe instrument panel duct 1 according to the present example, there areprovided the flange portions 103 (103 a to 103 g) and the bridgeportions 104 (104 e, 104 f). Accordingly, the instrument panel duct 1according to the present example can be affixed to other tubular membersat around the opening portions 100 and 111. In addition, the strengtharound the opening portions 100 and 111 can be increased. Nevertheless,the outer shape of the instrument panel duct 1 according to the presentexample as a whole may become complex. As a result, it may be difficultto take out the instrument panel duct 1 from the split mold blocks 12 aand 12 b.

(Other Exemplary Molding Methods)

The instrument panel duct 1 according to the foregoing example may bemolded by a molding method which will be described below with referenceto FIG. 8.

According to the molding method of FIG. 8, instead of the cylindricalfoamed parison 13 being extruded between the split mold blocks 12 a and12 b for molding by the above-described molding method, sheets of foamedresin are extruded between the split mold blocks 12 a and 12 b formolding.

As illustrated in FIG. 8, the molding device used by the other moldingmethod includes two extruding machines 50 a and 50 b as well as thesplit mold blocks 12 a and 12 b similar to those used by the precedingexemplary molding method.

The extruding machines 50 (50 a and 50 b) are disposed such that resinsheets P1 and P2 of foamed resin in molten state, including the samematerial as that of the foamed parison 13 used by the earlier exemplarymolding method, can droop substantially in parallel with a predeterminedinterval between the split mold blocks 12 a and 12 b. Under T-dies 28 aand 28 b for extruding the resin sheets P1 and P2, adjust rollers 30 aand 30 b are disposed. The adjust rollers 30 a and 30 b are used toadjust the thickness of the sheets, for example. The thus extruded resinsheets P1 and P2 are sandwiched and clamped between the split moldblocks 12 a and 12 b, whereby an instrument panel duct is molded.

The two extruding machines 50 (50 a and 50 b) have the sameconfiguration. Thus, one of the extruding machines 50 will be describedwith reference to FIG. 8.

The extruding machine 50 includes a cylinder 22 fitted with a hopper 21;a screw (not illustrated) disposed in the cylinder 22; a hydraulic motor20 coupled with the screw; an accumulator 24 internally in communicationwith the cylinder 22; a plunger 26 disposed in the accumulator 24; theT-die 28; and a pair of adjust rollers 30.

Resin pellets are fed from the hopper 21 into the cylinder 22, where thepellets are melted and kneaded by the screw rotated by the hydraulicmotor 20. Then, foamed resin in molten state is transported to theaccumulator 24. In the accumulator 24, a certain quantity of foamedresin is accumulated. As the plunger 26 is driven, the foamed resinfeeds out toward the T-die 28. Via an extrusion slit at the lower end ofthe T-die 28, a continuous sheet of the foamed resin in molten state isextruded. The resin sheet is sent downward while being compressedbetween the adjust rollers 30 disposed at an interval. The resin sheetthen droops between the split mold blocks 12 a and 12 b.

The T-die 28 is fitted with a die bolt 29 for adjusting the slitinterval of the extrusion slit. In addition to the die bolt 29, which isa mechanical unit, other slit interval adjusting mechanisms usingvarious known adjustment mechanisms may be employed.

By the above configuration, the resin sheets P1 and P2 having internalfoamed cells are extruded from the extrusion slits of the two T-dies 28a and 28 b. The sheets are adjusted to have a uniform thickness in thevertical direction (i.e., the direction of extrusion). The sheets thendroop between the split mold blocks 12 a and 12 b.

When the resin sheets P1 and P2 are thus disposed between the split moldblocks 12 a and 12 b, the split mold blocks 12 a and 12 b are advancedhorizontally until molds, not illustrated but positioned on the outerperiphery of the split mold blocks 12 a and 12 b, are closely attachedto the resin sheets P1 and P2. After the resin sheets P1 and P2 are heldby the molds on the outer periphery of the split mold blocks 12 a and 12b, the resin sheets P1 and P2 are suctioned by vacuum into the cavities10 a and 10 b of the split mold blocks 12 a and 12 b, whereby the resinsheets P1 and P2 each are given shapes conforming to the cavities 10 aand 10 b.

The split mold blocks 12 a and 12 b are then horizontally advanced andclamped and, as in the case of the molding method described earlier, theblow-in needle 14 and the blow-out needles 15 are pierced into the resinsheets P1 and P2. From the blow-in needle 14, compressed gas, such ascompressed air, is blown into the resin sheets P1 and P2. The compressedgas passes through the resin sheets P1 and P2 and is blown out of theblow-out needles 15. In this way, the inside of the portioncorresponding to the tube body X1 of the instrument panel duct 1 iscooled.

Thereafter, the split mold blocks 12 a and 12 b are withdrawnhorizontally and removed from the instrument panel duct 1.

The resin sheets P1 and P2 drooping between the pair of split moldblocks 12 a and 12 b may have thickness variations due to drawdown orneck-in, for example. Accordingly, in order to prevent this, it may benecessary to adjust the thickness of the resin sheet, extrusion speed,thickness distribution in the extrusion direction, and the likeindividually.

For such adjustments of the resin sheet thickness, extrusion speed,thickness in the extrusion direction and the like, various known methodsmay be used.

Thus, the instrument panel duct 1 according to the present example canalso be molded in a preferable manner by the other exemplary moldingmethod described with reference to FIG. 8, in the same way as accordingto the molding method described with reference to FIG. 4 to FIG. 6. Bythe other exemplary molding method of FIG. 8, the instrument panel duct1 adapted to various conditions can be molded by setting mutuallydifferent materials, expansion ratios, thicknesses and the like for thetwo resin sheets P1 and P2.

EXAMPLES

The instrument panel duct 1 will be described with reference to examplesand comparative examples. It should be noted, however, that the presentexample is not limited to the following examples.

Example 1

Foamed resin as raw material resin for the instrument panel duct 1 wasprepared by melting and kneading 50 parts by mass of resin A and 50parts by mass of resin B. A foamed blow molding machine equipped with ascrew-type extruder having a gas supply opening in a cylinder thereofwas used. Via the gas supply opening, supercritical fluid of nitrogenwas added. A sample of the instrument panel duct 1 having the same shapeas the instrument panel duct 1 illustrated in FIG. 1 was molded by thesame molding method as described with reference to FIG. 4 to FIG. 6;namely, by foamed blow molding, under the following molding conditions.

Resin A was a high-density polyethylene-based resin (B470 manufacturedby Asahi Kasei Chemicals Corp.; density=0.949 g/cm³, MFR=0.3 g/10 min at190° C., polymerization process=tubular process).

Resin B was a low-density polyethylene-based resin (Sumikathene G201Fmanufactured by Sumitomo Chemical Co., Ltd.; density=0.919 g/cm³,MFR=1.7 g/10 min, 190° C., polymerization process=autoclave process).

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 50 parts by mass of resin A to 50 parts by mass ofresin B was 1.00. Specifically, the value of MFR of the resin materialaccording to the blend ratio was calculated by finding a sum of the MFRof resin A (0.3) subjected to a calculation process using the blendratio (50%) (0.3×50/100=0.15) and the MFR of resin B (1.7) subjected toa calculation process using the blend ratio (50%) (1.7×50/100=0.85)(0.15+085=1.00).

Notes:

Molding Conditions:

Outer diameter of parison: 120 mm

Resin temperature at the exit of dies: 172° C.

Thickness of parison: 5 mm

Average thickness of instrument panel duct 1: 0.5 mm

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.40.

The expansion ratio of the molded instrument panel duct 1 was 4.3.

The surface roughness Rmax of the duct inner surface of the moldedinstrument panel duct 1 was not more than 200 μm. Accordingly, thesurface roughness was high (“Good”).

When the molded instrument panel duct 1 was taken out of the split moldblocks 12 a and 12 b, the foamed resin constituting the instrument panelduct 1 did not become attached to the split mold blocks 12 a and 12 b.Namely, the instrument panel duct 1 was easily taken out of the splitmold blocks 12 a and 12 b. Accordingly, the ease of removal was high(“Good”).

The burrs on the molded instrument panel duct 1 were easily removed.Accordingly, the ease of deburring was high (“Good”).

The value of MFR was measured at the test temperature of 190° C. andwith the test load of 2.16 kg according to JIS K-7210.

The value of expansion ratio was determined by dividing the density ofthe foamed resin used for molding the instrument panel duct 1 by theapparent density of the tube body X1 of the molded instrument panel duct1 (see FIG. 3).

The surface roughness Rmax indicates the maximum height measured using asurface roughness meter (SURFCOM 470A manufactured by Tokyo SeimitsuCo., Ltd.). The surface roughness was measured at all regions of theduct inner surface of the instrument panel duct 1. The surface roughnesswas evaluated by a method such that the surface roughness was consideredto be high (“Good”) when Rmax was not higher than 200 μm in all of theregions. When there was a portion with Rmax of higher than 200 μm, thesurface roughness was considered low (“Poor”).

The ease of removal was evaluated by a method such that the ease ofremoval was evaluated to be high (“Good”) if the foamed resinconstituting the instrument panel duct 1 did not become attached to thesplit mold blocks 12 a and 12 b when, after blow molding, the instrumentpanel duct 1 was removed from between the split mold blocks 12 a and 12b opened with the burrs formed on top of the instrument panel duct 1being gripped by a predetermined machine (such as clips), and thereforethe instrument panel duct 1 was easily taken out of the split moldblocks 12 a and 12 b. The ease of removal was evaluated to be low(“Poor”) if, when the instrument panel duct 1 was removed from betweenthe opened split mold blocks 12 a and 12 b, the foamed resinconstituting the instrument panel duct 1 became attached to the splitmold blocks 12 a and 12 b, so that the instrument panel duct 1 was movedby a predetermined distance or more together with the movement of thesplit mold blocks 12 a and 12 b. The ease of removal was also evaluatedto be low (“Poor”) if foamed resin remained on the split mold blocks 12a and 12 b. The burrs formed on top of the instrument panel duct 1 referto the portion of foamed resin protruding from the top of the split moldblocks 12 a and 12 b being clamped.

The ease of deburring was evaluated by a method such that, when theburrs formed around the instrument panel duct 1 taken out of the splitmold blocks 12 a and 12 b were partially cut with a cutter or the likeso as to remove the burrs by hand, for example, the ease of deburringwas evaluated to be high (“Good”) if the burrs were easily removed fromthe instrument panel duct 1. If the burrs became torn and remained onthe instrument panel duct 1 during attempted removal, or if theinstrument panel duct 1 was deformed during the removal of burrs, theease of deburring was evaluated to be low (“Poor”). The burrs may beformed around the parting line of the instrument panel duct 1, with athin portion formed between the instrument panel duct 1 and the burrs bypinch-off. The burrs are cut off at the thin portion.

Example 2

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 60 parts by mass of resin A and 40 parts by mass of resin B.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 60 parts by mass of resin A to 40 parts by mass ofresin B was 0.86.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.37.

The expansion ratio of the molded instrument panel duct 1 was 3.9.

The surface roughness, ease of removal, and ease of deburring were allhigh (“Good”).

Example 3

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 70 parts by mass of resin A and 30 parts by mass of resin B.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 70 parts by mass of resin A to 30 parts by mass ofresin B was 0.72.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.26.

The expansion ratio of the molded instrument panel duct 1 was 2.8.

The surface roughness, ease of removal, and ease of deburring were allhigh (“Good”).

Example 4

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 80 parts by mass of resin A and 20 parts by mass of resin B.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 80 parts by mass of resin A to 20 parts by mass ofresin B was 0.58.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.22.

The expansion ratio of the molded instrument panel duct 1 was 2.2.

The surface roughness, ease of removal, and ease of deburring were allhigh (“Good”).

Example 5

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 90 parts by mass of resin A and 10 parts by mass of resin B.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 90 parts by mass of resin A to 10 parts by mass ofresin B was 0.44.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.18.

The expansion ratio of the molded instrument panel duct 1 was 1.6.

The surface roughness, ease of removal, and ease of deburring were allhigh (“Good”).

Example 6

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 60 parts by mass of resin A and 40 parts by mass of resin C.

Resin C was a low-density polyethylene-based resin (CP763 manufacturedby Schulman; density=0.919 g/cm³, MFR=1.8 g/10 min at 190° C.,polymerization process=tubular process).

The MFR (190° C., g/10 min) of the foamed resin obtained by melting andkneading resin A and resin C was 0.9.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 60 parts by mass of resin A to 40 parts by mass ofresin C was 0.90.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.39.

The expansion ratio of the molded instrument panel duct 1 was 1.6.

The surface roughness, ease of removal, and ease of deburring were allhigh (“Good”).

Example 7

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 60 parts by mass of resin A and 40 parts by mass of resin D.

Resin D was a low-density polyethylene-based resin (Sumikathene F108-1manufactured by Sumitomo Chemical Company, Limited; density=0.921 g/cm³,MFR=0.4 g/10 min at 190° C., polymerization process=tubular process).

The MFR (190° C., g/10 min) of the foamed resin obtained by melting andkneading resin A and resin D was 0.34.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 60 parts by mass of resin A to 40 parts by mass ofresin D was 0.34.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.17.

The expansion ratio of the molded instrument panel duct 1 was 1.3.

The surface roughness, ease of removal, and ease of deburring were allhigh (“Good”).

Example 8

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 100 parts by mass of resin D.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 100 parts by mass of resin D was 0.40.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.18.

The expansion ratio of the molded instrument panel duct 1 was 1.6.

The surface roughness, ease of removal, and ease of deburring were allhigh (“Good”).

Comparative Example 1

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 100 parts by mass of resin B.

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 100 parts by mass of resin B was 1.70.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was0.80.

The expansion ratio of the molded instrument panel duct 1 was 5.0.

The surface roughness Rmax of the duct inner surface of the moldedinstrument panel duct 1 was not more than 200 μm. Accordingly, thesurface roughness was high (“Good”).

When the molded instrument panel duct 1 was taken out of the split moldblocks 12 a and 12 b, the foamed resin constituting the instrument panelduct 1 became attached to the split mold blocks 12 a and 12 b, andtherefore the instrument panel duct 1 was not easily taken out of thesplit mold blocks 12 a and 12 b. Accordingly, the ease of removal waslow (“Poor”).

The burrs on the molded instrument panel duct 1 were not easily removed.Accordingly, the ease of deburring was low (“Poor”).

Comparative Example 2

The instrument panel duct 1 was molded by the same method as accordingto example 1 with the exception that the foamed resin as raw materialresin of the instrument panel duct 1 was prepared by melting andkneading 60 parts by mass of resin E and 40 parts by mass of resin B.

Resin E was a high-density polyethylene-based resin (J240 manufacturedby Asahi Kasei Chemicals Corp.; density=0.966 g/cm³, MFR=5.0 g/10 min at190° C., polymerization process=tubular process).

The MFR (190° C., g/10 min) of the resin material calculated accordingto the blend ratio of 60 parts by mass of resin E to 40 parts by mass ofresin B was 3.68.

The MFR (190° C., g/10 min) of the molded instrument panel duct 1 was3.20.

The expansion ratio of the molded instrument panel duct 1 was 4.3.

The surface roughness Rmax of the duct inner surface of the moldedinstrument panel duct 1 was partly higher than 200 μm. Accordingly, thesurface roughness was low (“Poor”).

When the molded instrument panel duct 1 was taken out of the split moldblocks 12 a and 12 b, the foamed resin constituting the instrument panelduct 1 became attached to the split mold blocks 12 a and 12 b, andtherefore the instrument panel duct 1 was not easily taken out of thesplit mold blocks 12 a and 12 b. Accordingly, the ease of removal waslow (“Poor”).

The burrs on the molded instrument panel duct 1 were not easily removed.Accordingly, the ease of deburring was low (“Poor”).

FIG. 9 shows the test results for examples 1 to 8 and comparativeexamples 1 and 2. Specifically, FIG. 9 shows the blend ratios of theresin material used when molding the instrument panel duct 1 accordingto examples 1 to 8 and comparative examples 1 and 2; the MFRs of theresin material calculated according to the blend ratios; the MFRs of themolded instrument panel duct 1; and the expansion ratios, surfaceroughness, ease of removal, and ease of deburring of the moldedinstrument panel duct 1.

As shown in FIG. 9, it was learned that the instrument panel duct 1having high surface roughness, ease of removal, and ease of deburringwas obtained when the MFR of the molded instrument panel duct 1 was setto be less than 0.8, or when the MFR of the resin material calculatedaccording to the blend ratio was set to be not more than 1.0.

It was also learned that the instrument panel duct 1 having highexpansion ratios can be obtained by using foamed resin obtained bymixing high-density polyethylene-based resin and low-densitypolyethylene-based resin.

Further, it was learned that the instrument panel duct 1 having highexpansion ratios can be obtained by using foamed resin obtained bymixing polyethylene-based resin manufactured by autoclave process.

It was additionally learned that the instrument panel duct 1 having highsurface roughness, ease of removal, and ease of deburring can beobtained by using low-density polyethylene-based resin with the MFR of1.0 to 3.0, and by setting the MFR of the molded instrument panel duct 1to be less than 0.8 or by setting the MFR of the resin materialcalculated according to the blend ratio to be not more than 1.0.

The foregoing example is a preferable example of the present invention,and the present invention is not limited to such example. Variousmodifications of the present invention may be implemented based on thetechnical concept of the present invention.

While the example has been described with reference to the instrumentpanel duct 1, the present invention may also be applied to, e.g., a rearair-conditioner duct and the like.

The invention claimed is:
 1. A blow molded foam molded from a foamedresin made of a polyethylene-based resin, the blow molded foam being anautomobile duct configured to circulate cool or warm aft supplied froman air conditioning unit, wherein the blow molded foam has a MFR (190°C., g/10 min) of not less than 0.17 and not more than 0.40, and whereina surface roughness Rmax of the blow molded foam is 200 μm or less,wherein the polyethylene-based resin has a MFR (190° C., g/10 min) ofnot less than 0.34 and not more than 1.0, wherein the polyethylene-basedresin consists of: a high-density polyethylene-based resin of between 50parts by mass and 90 parts by mass, wherein the high-densitypolyethylene-based resin has a density 0.949 g/cm³, a MFR of 0.3 g/10min, and a low-density polyethylene-based resin of between 10 parts bymass and 50 parts by mass, wherein the low-density polyethylene-basedresin has a density 0.919 g/cm³, a a MFR of 1.7 g/10 min.
 2. The blowmolded foam molded according to claim 1, wherein the low-densitypolyethylene-based resin is manufactured by an autoclave process.
 3. Theblow molded foam according to claim 1, wherein the polyethylene-basedresin consists of the high-density polyethylene-based resin of 50 partsby mass and the low-density polyethylene-based resin of 50 parts bymass.
 4. The blow molded foam according to claim 1, comprising a tubebody having a supply portion to be connected to an air conditioner unit;and tube portions with one end connected to the supply portion and otherend provided with fitting portions, and flange portions connected to thetube body, wherein the automobile duct is configured to circulate coolor warm air supplied from the supply portion into the tube body.
 5. Theblow molded foam molded according to claim 1, wherein thepolyethylene-based resin has a MFR (190° C., g/10 min) of 0.34 to 0.9.6. The blow molded foam molded according to claim 1, wherein thepolyethylene-based resin has a MFR (190° C., g/10 min) of not less than0.44 and not more than 1.0.